Biomedical subjects

Shigeki Jinno

Publications and source records attributed to Shigeki Jinno.

5 recordsLinked to original sources

PubMed2004

Bone morphogenetic protein 2-induced osteoblast differentiation requires Smad-mediated down-regulation of Cdk6.

Because a temporal arrest in the G(1) phase of the cell cycle is thought to be a prerequisite for cell differentiation, we investigated cell cycle factors that critically influence the differentiation of mouse osteoblastic MC3T3-E1 cells induced by bone morphogenetic protein 2 (BMP-2), a potent inducer of osteoblast differentiation. Of the G(1) cell cycle factors examined, the expression of cyclin-dependent kinase 6 (Cdk6) was found to be strongly down-regulated by BMP-2/Smads signaling, mainly via transcriptional repression. The enforced expression of Cdk6 blocked BMP-2-induced osteoblast differentiation to various degrees, depending on the level of its overexpression. However, neither BMP-2 treatment nor Cdk6 overexpression significantly affected cell proliferation, suggesting that the inhibitory effect of Cdk6 on cell differentiation was exerted by a mechanism that is largely independent of its cell cycle regulation. These results indicate that Cdk6 is a critical regulator of BMP-2-induced osteoblast differentiation and that its Smads-mediated down-regulation is essential for efficient osteoblast differentiation.

Animals↗

PubMed2003

Overexpression of Cdk6-cyclin D3 highly sensitizes cells to physical and chemical transformation.

Virtually all mammalian cells express two seemingly redundant cyclin-D-dependent kinases (Cdk4 and Cdk6) and three partner cyclins (D1, D2 and D3) essential for the G(1)-S transition, with predominant expression of Cdk4 and D1 in mesenchymal cells and Cdk6 and D3 in hematopoietic cells. We recently found two novel functions for Cdk6 executed in fibroblasts although unlike Cdk4 it is dispensable for their proliferation. In the rat fibroblast NRK-49F cells, oncogenic stimulation recruits Cdk6 to participate in a step of the cell cycle start that seems to be critical for anchorage-independent S-phase onset. Among the kinase-D-type cyclin combinations, the Cdk6-cyclin-D3 complex has a unique ability to evade inhibition by cyclin-dependent kinase inhibitors and thereby control the cell's proliferative competence under growth-suppressive conditions. We describe here that 2-5-fold overexpression of both Cdk6 and D3 enhances by 5x10(3)-10(6)-fold the susceptibility of the BALB/c3T3 and C3H10T1/2 mouse fibroblast lines to ultraviolet irradiation- as well as 3-methylcholanthrene-induced transformation. This result suggests that deregulated expression of Cdk6 and cyclinD3 may predispose cells to malignant transformation, supporting the recent finding that cyclin D3 activated by chromosomal rearrangement is the causative gene of non-Hodgkin B lymphoma, in which Cdk6 is the major partner kinase.

Amino Acid Substitution↗

PubMed2002

Mammalian Rcd1 is a novel transcriptional cofactor that mediates retinoic acid-induced cell differentiation.

Rcd1, initially identified as a factor essential for the commitment to nitrogen starvation-invoked differentiation in fission yeast, is one of the most conserved proteins found across eukaryotes, and its mammalian homolog is expressed in a variety of differentiating tissues. Here we show that mammalian Rcd1 is a novel transcriptional cofactor and is critically involved in the commitment step in the retinoic acid-induced differentiation of F9 mouse teratocarcinoma cells, at least in part, via forming complexes with retinoic acid receptor and activation transcription factor-2 (ATF-2). In addition, antisense oligonucleotide treatment of embryonic mouse lung explants suggests that Rcd1 also plays a role in retinoic acid-controlled lung development.

Animals↗

PubMed2002

Cdc6 requires anchorage for its expression.

Fibroblasts need anchorage to extracellular matrix to transit from G1 to S phase, but no longer after oncogenic transformation. Here we report that Cdc6 protein essential for the activation of replication origins requires anchorage or oncogenic stimulation for its execution. Upon anchorage loss, Cdc6 expression is shut off both transcriptionally and post-transcriptionally in a rat fibroblast despite enforced activation of E2F-dependent promoters. However, stimulation of this cell with oncogenic growth factors suppresses this shutoff and concurrently activates Cdk2 and Cdk6/4, thereby overriding the anchorage requirement for the G1-S transition and consequently enabling cells to perform anchorage-independent S phase entry. Analysis with enforced expression of Cdc6 indicates that the G1 cyclin-dependent kinases and Cdc6 constitute major cell cycle targets for the restriction of the G1-S transition by anchorage loss.

Animals↗

PubMedDate not supplied

Nonviral gene delivery by tetraamino fullerene.

A fullerene derivative bearing two diamino side chains binds to a plasmid vector DNA, either 4 or 40 kbp in size, delivers it to mammalian cells on incubation, and leads to expression of the encoded gene either transiently or stably. The initial physicochemical investigations upon DNA-binding and protective properties of various fullerene compounds against nuclease led us to identify the tetraamino fullerene as an ideal candidate to probe the new concept of fullerene-mediated gene delivery to mammalian cells. Studies on transient and stable transfection of COS-1 cells using green fluorescent protein and luciferase reporter genes revealed several useful properties of the fullerene transfection as compared with the conventional lipid-based transfection method, including much higher efficiency of stable transfection and ability to transfect confluent cells. Chemical and biological studies suggested that the cell uptake of the fullerene/DNA complex takes place by an endocytosis mechanism and that the DNA internalized by endosomes is protected by the fullerene against enzymatic digestion. The stiffness of the fullerene/DNA complex may play some role in the success of the fullerene method.

Animals↗